1. Field of the Invention
The present invention relates to methods for adjusting the contrast of a display device and to devices having a function for adjusting the contrast of the display device, and more particularly relates to a method and to a device having a function for adjusting the display contrast of a liquid crystal display (LCD) or the like incorporated in a portable information apparatus, such as an electronic notebook or a personal digital assistant (PDA).
2. Description of the Related Art
Hitherto, in a portable information apparatus or the like having an LCD, such as an electronic notebook or a PDA, adjustment of the contrast of the LCD is sometimes required when the battery is changed. In order to reduce the number of parts and the production cost of the apparatus, instead of an external mechanical contrast-adjustment member, an electronic contrast-adjustment member has been used to adjust the contrast of the LCD. However, since the electronic contrast adjustment member is set using a graphical user interface (GUI) icon displayed on the LCD, a confirmation operation or the like cannot be performed in a case in which the screen is displayed at an inappropriate contrast.
To solve the problems, there has been proposed “Display State Setting Apparatus” as disclosed in Japanese Patent Laid-Open No. 7-110663 in which, when a display device is turned on, the display driving voltage level is automatically changed and is set by stopping the change in the driving voltage by a predetermined operation, such as by a key input.
However, in the above conventional technique, since a user can only stop the progressive change in the display driving voltage level, an appropriate contrast for the display device is difficult to set.
Furthermore, since it is desired to adjust the contrast of the display device not only during the start-up processing but also after a long period of use of the display device, the display contrast adjustment should be performable even after the start-up processing and should be easily performed.